| 1. |
- Amada, K., et al.
(författare)
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Discovery of SiO Masers in the "Water Fountain" Source IRAS 16552-3050
- 2022
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 163:2
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report new detections of SiO v = 1 and v = 2 J = 1 -> 0 masers in the "water fountain" source IRAS 16552-3050, which was observed with the Nobeyama 45 m telescope during 2021 March-April. Water fountains are evolved stars whose H2O maser spectra trace high-velocity outflows of >100 km s(-1). This is the second known case of SiO masers in a water fountain, after their prototypical source, W 43A. These SiO masers should shed light on the evolutionary status of this category of evolved stars, which are likely to be at the end of the asymptotic giant branch phase, when the star exhibits the most copious stellar mass loss, followed by development of the complicated morphologies of planetary nebulae. The origin of a large (up to 25 km s(-1)) velocity offset of the SiO masers with respect to the systemic velocity derived from the spectrum of CO J = 2 -> 1 line is discussed here.
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| 2. |
- Amada, Kei, et al.
(författare)
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Discovery of SiO masers in the Water Fountain source, IRAS 16552-3050
- 2022
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 18, s. 359-361
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Konferensbidrag (refereegranskat)abstract
- We report new detections of SiO ν = 1 and ν = 2 J = 1 → 0 masers in the water fountain source IRAS 16552-3050, which was observed with the Nobeyama 45 m telescope from March 2021 to April 2023. Water fountains are evolved stars whose H2O maser spectra trace high-velocity outflows of >100 Km s-. This is the second known case of SiO masers in a water fountain, after their prototypical source, W 43A. The line-of-sight velocity of the SiO masers are blue-shifted by ∼25 km s-1 from the systemic velocity. This velocity offset imply that the SiO masers are associated with nozzle structure formed by a jet penetrating the circumstellar envelope, and that new gas blobs of the jet erupted recently. Thus, the SiO masers imply this star to be in a new evolutionary stage.
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| 3. |
- Ceccobello, Chiara, 1984, et al.
(författare)
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A study of radial self-similar non-relativistic MHD outflow models: parameter space exploration and application to the water fountain W43A
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 501:2, s. 2071-2090
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Tidskriftsartikel (refereegranskat)abstract
- Outflows, spanning a wide range of dynamical properties and spatial extensions, have now been associated with a variety of accreting astrophysical objects, from supermassive black holes at the core of active galaxies to young stellar objects. The role of such outflows is key to the evolution of the system that generates them, for they extract a fraction of the orbiting material and angular momentum from the region close to the central object and release them in the surroundings. The details of the launching mechanism and their impact on the environment are fundamental to understand the evolution of individual sources and the similarities between different types of outflow-launching systems. We solve semi-analytically the non-relativistic, ideal, magnetohydrodynamics equations describing outflows launched from a rotating disc threaded with magnetic fields using our new numerical scheme. We present here a parameter study of a large sample of new solutions. We study the different combinations of forces that lead to a successfully launched jet and discuss their global properties. We show how these solutions can be applied to the outflow of the water fountain W43A for which we have observational constraints on magnetic field, density and velocity of the flow at the location of two symmetrical water maser emitting regions.
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| 4. |
- Chong, S. N., et al.
(författare)
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Multipolar Planetary Nebulae: Not As Geometrically Diversified As Thought
- 2012
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 760:2
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Tidskriftsartikel (refereegranskat)abstract
- Planetary nebulae (PNe) have diverse morphological shapes, including point-symmetric and multipolar structures. Many PNe also have complicated internal structures such as tori, lobes, knots, and ansae. A complete accounting of all the morphological structures through physical models is difficult. A first step toward such an understanding is to derive the true three-dimensional structure of the nebulae. In this paper, we show that a multipolar nebula with three pairs of lobes can explain many such features, if orientation and sensitivity effects are taken into account. Using only six parameters-the inclination and position angles of each pair-we are able to simulate the observed images of 20 PNe with complex structures. We suggest that multipolar structure is an intrinsic structure of PNe and the statistics of multipolar PNe have been severely underestimated in the past.
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| 5. |
- De La Fuente, Eduardo, et al.
(författare)
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Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
- 2023
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Ingår i: Publication of the Astronomical Society of Japan. - 2053-051X .- 0004-6264. ; 75:3, s. 546-566
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Tidskriftsartikel (refereegranskat)abstract
- PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star clusters is essential to clarify the underlying nature of the PeV emission, i.e., hadronic or leptonic. We present 12,13CO (J = 2→1) observations made with the 1.85 m radio-Telescope of the Osaka Prefecture University toward the Cygnus OB7 molecular cloud, which contains the PeVatron candidate LHAASO J2108+5157. We investigate the nature of the sub-PeV (gamma-ray) emission by studying the nucleon density determined from the content of H i and H2, derived from the CO observations. In addition to MML[2017]4607, detected via the observations of the optically thick 12CO (J = 1→0) emission, we infer the presence of an optically thin molecular cloud, named [FKT-MC]2022, whose angular size is 1-1 ± 0.}^\circ}}2. We propose this cloud as a new candidate to produce the sub-PeV emission observed in LHAASO J2108+5157. Considering a distance of 1.7 kpc, we estimate a nucleon (H i + H2) density of 37 ± 14 cm-3, and a total nucleon mass(H i + H2) of 1.5 ± 0.6 × 104 M·. On the other hand, we confirm that Kronberger 82 is a molecular clump with an angular size of 0°1, a nucleon density ∼103 cm-3, and a mass ∼103 M·. Although Kronberger 82 hosts the physical conditions to produce the observed emission of LHAASO J2108+5157, [FKT-MC]2022 is located closer to it, suggesting that the latter could be the one associated to the sub-PeV emission. Under this scenario, our results favour a hadronic origin for the emission.
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| 6. |
- De La Fuente, Eduardo, et al.
(författare)
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Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 675
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Tidskriftsartikel (refereegranskat)abstract
- Context . Peta-eV (PeV) astronomy emerged in 2021 with the discovery of ultra-high-energy gamma-ray sources associated with powerful natural particle accelerators known as PeVatrons. In order to determine the nature of their emission, namely whether it has a hadronic or leptonic origin, it is essential to characterise the physical parameters of the environment where it originates. Aims . We unambiguously confirm the association of molecular gas with the PeVatron candidate LHAASO J2108+5157 using unprecedented high angular-resolution (17′) 12,13CO(J = 1 → 0) observations carried out with the Nobeyama 45m radio telescope. Methods . We characterised a molecular cloud in the vicinity of the PeVatron candidate LHAASO J2108+5157 by determining its physical parameters from our 12,13CO(J = 1 → 0) line observations. We used an updated estimation of the distance to the cloud, which provided a more reliable result. The molecular emission was compared with excess gamma-ray images obtained with Fermi-LAT at energies above 2 GeV to search for spatial correlations and test a possible hadronic (π0 decay) origin for the gamma-ray emission. Results . We find that the morphology of the spatial distribution of the CO emission is strikingly similar to that of the Fermi-LAT excess gamma ray. By combining our observations with archival 21 cm HI line data, the nucleons (HI + H2) number density of the target molecular cloud is found to be 133.0 ± 45.0 cm-3, for the measured angular size of 0.55 ± 0.02 at a distance of 1.6 ± 0.1 kpc. The resulting total mass of the cloud is M(HI + H2) = 7.5±2.9×103M⊙. Under a hadronic scenario, we obtain a total energy of protons of Wp = 4.3 ± 1.5 × 1046 erg with a cutoff of 700±300 TeV, which reproduces the sub-PeV gamma-ray emission. Conclusions . We identified a molecular cloud in the vicinity of LHAASO J2107+5157 as the main target where cosmic rays from an unknown PeVatron produce the observed gamma-ray emission via π0 decay.
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| 7. |
- de la Fuente, Eduardo, et al.
(författare)
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The symbiotic and bipolar nebula M2-9: Morphological variability of the collimated ionized wind arising from the core
- 2022
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 74:3, s. 594-601
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Tidskriftsartikel (refereegranskat)abstract
- We studied the central region of bipolar nebula M 2-9 using radio-continuum observations obtained from the Jansky Very Large Array (JVLA) and the Atacama Large Millimeter Array (ALMA) interferometers. This work presents new images at similar to 43 GHz (similar to 7.0 mm) and similar to 345 GHz (similar to 0.9 mm) with angular resolutions of similar to 0 ''.047 and 0 ''.09, respectively. The continuum emission at similar to 43 GHz shows an elongated jet-like structure perpendicular to the similar to 345 GHz observation. We conclude that both emissions could correspond to tracing an isothermal collimated fast wind with constant expansion velocity and being driven by the circumstellar ring traced by ALMA. Although this configuration has been discussed within the scope of planetary nebulae models, there is a remarkable fact: the collimated fast wind shows morphological spatial variability. This supports the idea of a symbiotic binary system within the innermost part of M 2-9, which would be composed of a white dwarf and an AGB star. The latter could explain the mirror symmetry observed at larger scales due to their orbital motion.
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| 8. |
- de la Fuente, Eduardo, et al.
(författare)
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Ultracompact H II regions with extended emission: the case of G43.89-0.78 and its molecular environment
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 497:4, s. 4436-4447
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Tidskriftsartikel (refereegranskat)abstract
- The Karl Jansky Very Large Array (VLA), Owens Valley Radio Observatory (OVRO), Atacama Large Millimetric Array (ALMA), and the infrared Spitzer observatories are powerful facilities to study massive star formation regions and related objects such as ultra-compact (UC) H II regions, molecular clumps, and cores. We used these telescopes to study the UC H II region G43.89-0.78. The morphological study at arcminute scales using NVSS and Spitzer data shows that this region is similar to those observed in the bubble-like structures revealed by Spitzer observations. With this result, and including a physical characterization based on 3.6 cm data, we suggest G43.89-0.78 be classified as an UC H II region with Extended Emission because it meets the operational definition given in this paper comparing radio continuum data at 3.6 and 20 cm. For the ultra-compact component, we use VLA data to obtain physical parameters at 3.6 cm confirming this region as an UC H II region. Using ALMA observations, we detect the presence of a dense (2.6 x 10(7) cm(-3)) and small (similar to 2.0 arcsec; 0.08 pc) molecular clump with a mass of 220 M-circle dot and average kinetic temperature of 21 K, located near to the UC H II region. In this clump, catalogued as G43.890-0.784, water masers also exist, possibly tracing a bipolar outflow. We discover in this vicinity two additional clumps which we label as G43.899-0.786 (T-d = 50 K; M = 11 M-circle dot) and G43.888-0.787 (T-d = 50 K; M = 15 M-circle dot).
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| 9. |
- De La Fuente, Eduardo, et al.
(författare)
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Ultracompact HII regions with extended emission: The complete view
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 492:1, s. 895-914
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 The Author(s). In this paper, we present the results of a morphological study performed on a sample of 28 ultracompact HII (UC HII) regions located near extended free-free emission, using radio continuum (RC) observations at 3.6 cm with the C and D Very Large Array (VLA) configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA configurations, we compiled a final catalogue of 21 UC HII regions directly connected with the surrounding extended emission (EE). The observed morphology of most of the UC HII regions in RC emission is irregular (single- or multipeaked sources) and resembles a classical bubble structure in the Galactic plane with well-defined cometary arcs. RC images superimposed on colour composite Spitzer images reinforce the assignations of direct connection by the spatial coincidence between the UC components and regions of saturated 24 μm emission. We also find that the presence of EE may be crucial to understand the observed infrared excess because an underestimation of ionizing Lyman photons was considered in previous works (e.g. Wood & Churchwell; Kurtz, Churchwell & Wood).
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| 10. |
- Imai, H., et al.
(författare)
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FLASHING: New high-velocity H2O masers in IRAS 18286−0959
- 2020
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 72:4
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Tidskriftsartikel (refereegranskat)abstract
- We discovered new high-velocity components of H2O maser emission in one of the “water fountain” sources, IRAS 18286−0959, which has been monitored using the Nobeyama 45 m telescope in the FLASHING (Finest Legacy Acquisitions of SiO- and H2O-maser Ignitions by Nobeyama Generation) project since 2018 December. The maser spectra show new components with extremely high expansion velocities (>200 km s−1 projected in the line of sight), some of which are located symmetrically in the spectrum with respect to the systemic velocity. They were also mapped with KaVA (KVN and VERA Combined Array) in 2019 March. We located some of these maser components closer to the central stellar system than other high-velocity components (50-200 km s−1) that have been confirmed to be associated with the known bipolar outflow. The new components would have flashed in the fast collimated jet at a speed of over 300 km s−1 (soon) after 2011 when they had not been detected. The fastest of the new components seem to indicate rapid deceleration in these spectra; however, our present monitoring is still too sparse to unambiguously confirm it (up to 50 km s−1 yr−1) and too short to reveal their terminal expansion velocity, which will be equal to the expansion velocity that has been observed (vexp ∼ 120 km s−1). Future occurrences of such extreme-velocity components may provide a good opportunity to investigate possible recurrent outflow ignitions. Thus, the sculpture of the parental envelope will be traced by the dense gas that is entrained by the fast jet and exhibits spectacular distributions of the relatively stable maser features.
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